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Understanding Carbon Nanotubes: Properties, Growth, and Applications

Explore the structure, properties, growth methods, and applications of carbon nanotubes, including electronic and optical features, quantum confinement, chirality, and phonon vibrations. Learn about nanotube growth techniques and their industrial-scale production.

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Understanding Carbon Nanotubes: Properties, Growth, and Applications

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  1. Carbon nanotubes Stephanie Reich Fachbereich Physik, Freie Universität Berlin

  2. Pure sp2 & sp3 carbon 1991 iron age 2004 4 cen BC 1985

  3. Single-walled carbon nanotubes • Nanotubes are not one, but many materials • Nanotubes consist only of surface atoms diameter: 1 – 5 nm, length: up to cm U. Bristol

  4. Single-walled carbon nanotubes • Growth of carbon nanotubes • Zone folding & fundamentals • Electronic properties • Optical properties • Nanotube vibrations • (Functionalization)

  5. Nanotube growth • grow out of a carbon plasma • laser ablation • arc discharge • chemical vapor deposition • metal catalysts • nickel, cobalt, iron … • carbon tubes • diameter ~ 1 nm • length 500 nm – 4 cm • industrial scale production • started 2005 • since 2009 large scale http://home.hanyang.ac.kr/, www.seas.upenn.edu

  6. Chemical vapor deposition • long tubes & high yield • high quality • high degree of control during growth Hata, Science (2004); Zhang, Nat Mat (2004); Milne

  7. Nanotube growth • grow out of a carbon plasma • laser ablation • arc discharge • chemical vapor deposition • metal catalysts • nickel, cobalt, iron … • carbon tubes • diameter ~ 1 nm • length 500 nm – 4 cm • industrial scale production • started 2005 • since 2009 large scale http://home.hanyang.ac.kr/, www.seas.upenn.edu

  8. Nanotube structure • nanotube diameter d & chiral angle Θ determine microscopic structure Carbon nanotubes (Wiley, 2004) , Freitag group

  9. Nanotube structure • nanotube diameter d & chiral angle Θ determine microscopic structure Carbon nanotubes (Wiley, 2004)

  10. Chiral vector - (n,m) nanotube • nanotube diameter d & chiral angle Θ determine microscopic structure • specified by the chiral vector c around the circumference c = na1 + ma2 = 8 a1 + 8 a2 a2 a1 Carbon nanotubes (Wiley, 2004)

  11. Chiral vector - (10,0) nanotube • nanotube diameter d & chiral angle Θ determine microscopic structure • specified by the chiral vector c around the circumference c = na1 + ma2 = 10 a1 a2 a1 Carbon nanotubes (Wiley, 2004)

  12. Nanotube structure • typical samples contain 40 – 100 different chiralities • controlling chirality during growth is impossible (8,8) (6,6) (10,0) (8,3) Carbon nanotubes (Wiley, 2004)

  13. Quantum confinement • circumference – periodic boundary conditions •  = p diameter/p (p integer) Carbon nanotubes (Wiley, 2004)

  14. Confined phase space K  M Carbon nanotubes (Wiley, 2004)

  15. One-dimensional Brillouin zone Carbon nanotubes (Wiley, 2004)

  16. Band structure (10,0) tube Carbon nanotubes (Wiley, 2004)

  17. quantization in (n,0) n+1 allowed lines between G and M G K = 2/3 KM = 1/3 metals(3,0), (6,0), (9,0), (12,0) … semiconductors(2,0), (4,0), (5,0), (7,0) … general conditionmetallic if (n-m)/3 = integer Metal or semiconductor? – (n-m)/3 (10,0) semiconductor (9,0) metal Carbon nanotubes (Wiley, 2004)

  18. Metal & semiconductor in experiment E k

  19. Concept of zone folding • quantization along the circumference • reduced phase space • find nanotube properties by reference to graphene • works for • electrons, phonons, and other quasi-particles • interactions, e.g., electron-phonon coupling • central concept of nanotube research

  20. Graphene – a semimetal • valence and conduction band touch in a single point Reich, Carbon nanotubes (Wiley, 2004)

  21. HOMO & LUMO • HOMO & LUMO are degenerate • Nanotube chiral vector compatible with HOMO/LUMO wave function? Reich, Carbon nanotubes (Wiley, 2004)

  22. Metal or not? • three nanotube families metal semiconductor small gap semiconductor large gap

  23. Electronic properties of nanotubes • quantum confinement • band gap depends on structure • most properties depend on band gap E k metal semiconductors

  24. Optical properties of nanotubes • Every nanotube – colorful • Bulk nanotube samples – black

  25. Transitions between subbands valence conduction

  26. Chirality from luminescence • every (n,m) nanotube has specific pairs of transition energy • use this for assignment Bachilo, Science (2002)

  27. (6,6) (8,4) (10,0) Chirality from luminescence ? • luminescence detects semiconducting tubes, metallic not • some tubes were not observed Bachilo, Science (2002)

  28. Nanotubes, optics & excitons • chirality, electron-electron, and electron-hole interaction • sensitive to environment E. Malic, M. Hirtschulz

  29. Phonons in carbon nanotubes • 100 – 1000 vibrations • strong coupling to electronic system • radial-breathing mode (RBM) • high-energy mode (HEM) • D mode • twiston and low-energy phonons RBM HEM D mode Raman scattering on carbon nanotubes (Springer, 2006)

  30. Phonons in carbon nanotubes • 100 – 1000 vibrations • strong coupling to electronic system • radial-breathing mode (RBM) • high-energy mode (HEM) • D mode • twiston and low-energy phonons • characterizie nanotubes • presence • metallic/semiconductor • chirality RBM RBM HEM HEM D mode D mode

  31. Electron-phonon coupling • doping hardens phonon frequencies • metallic into semiconducting spectrum? • bundling effect? semiconducting metallic H. Farhat

  32. Phonon softening • vibration periodically opens and closes a band gap • softening of the phonon frequencies • phonon dispersion is singular • q = k1 – k2 Kohn (1959)

  33. Phonons limit nanotube transport • ballistic transport • resistance approaches quantum limit 13kΩ/channel • no scattering by defects • ballistic transport breaks down by hot phonons • phonon emission faster than decay Yang PRL (2000); Javey Science (2003)

  34. Functionalization • change nanotube properties • solubility • composite materials • sensitivity & reactivity • tune pristine properties • electron interaction • defects • vibrations

  35. Summary • Nanotube properties depend on their structure;there is no „typical nanotube“ • Growth of carbon nanotubes produces many different tubes = different materials • Nanotube absorb light & show infrared luminescence • Particularly strong electron-phonon coupling • Functionalize nanotubes for further tailoring

  36. Thanks to… • Cinzia Casiraghi (AvH)Antonio Setaro (FUB)Vitalyi Datsyuk (BmBF) • Rohit Narula (FUB)Sebastian Heeg (ERC)Oliver Schimek (DFG)Asaf Avnon (SfB)Thomas Straßburg (BmBF)Stefan Arndt (BmBF) • Ermin Malić (SfB)Megan Brewster (MIT, NSF) • TU BerlinChristian ThomsenJaninaMaultzsch • MITMichael StranoFrancesco StellacchiJing Kong • KITFrank Hennrich • University of CambridgeStefan HofmannJohn Robertson

  37. The end Thank you!

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